In recent years, basic level physiological and pharmacological studies have revealed a previously unsuspected diversity in inhibitory processes in cerebral cortex. Recent anatomical and immunocytochemical studies have revealed an equally diverse assortment of neurons that are good candidates for mediating these inhibitory events, but thus far there has been little progress in matching of the morphological substrate with physiological processes. Furthermore, there has been little analysis of the functional role of inhibitory processes either at the level of integrative processes in single neurons or at the level of information processing by systems of neurons. With these deficiencies in mind, the proposed experiments will examine inhibitory processes in the piriform cortex, a phylogenetically old part of the cerebral cortex that has a convenient segragation of different types of probable inhibitory interneurons at different depths and locations - a feature that will facilitate analysis of their physiological properties. In addition, there is a precise complementary lamination of fiber systems in piriform cortex - a feature that will facilitate study of the role of inhibition in integrative processes. Experimental approaches will include an analysis of inhibitory events and their interactions with excitatory events in pyramidal cells (principal cell type in cerebral cortex) by intracellular recording of potentials in brain slices maintained in vitro and by computation of the spatial and temporal distribution of the membrane currents that generate these potentials with the current source density technique in an in vivo preparation. The three populations of interneurons that have been postulated to mediate the different types of inhibitory processes observed in pyramidal cells will be studied with a combined physiological-morphological-immunocytochemical approach in the in vitro slice preparation. Direct analysis of synaptic effects mediated by these neurons on pyramidal cells will be carried out in cell pair intracellular stimulation-recording experiments.